Conveyor



Sept. 17, 1963 E. w. SWEZEY ETAL 3,104,007

I CONVEYOR Original Filed June 9, 1955 5 Sheets-Sheet l IN VE N TOR S W JW 4% Se t. 17, 1963 E. w. SWEZEY ETAL 3,104,007

CONVEYOR Original Filed June 9, 1955 5 Sheets-Sheet 2 10 Fig 5 lo INV'NTORS M W I QM 7 Sept. 17,1963 E. w. SWEZEY ETAL I 3,104,007

CONVEYOR Original Filed June 9, 1955 5 Sheets-Sheet 5 x/vvc/v TORS "I Sept. 17, 1963 E. w. SWEZEY ETAL 3,104,007

CONVEYOR 5 Sheets-Sheet 4 Original Filed June 9, 1955 3,2 0 C) O & f g

Sept. 17, 1963 E. w. SWEZEY ETAL 3,104,007

I CONVEYOR v Original Filed June 9, 1955 5 Sheets-Sheet 5 v a, /2/ [/1 F 9 N z\ I t I 0 O m 7 3 9 I03 13 [oz [0/ C5 93 United States Patent 3,104,007 CONVEYOR Edwin W. Swezey,.Hackensack, and Robert J. McKnight,

Upper Montclair, NJ assignors to The Rapids-Standard Company, Inc., Grand Rapids, Mich, a corporation of Michigan Original application June 9, 1955, Ser. No. 514,228, now Patent No. 2,895,593, dated'July 21, 1959. Divided and this application Mar. 17, 1959, Ser. No. 800,054

' 11 Claims. (Cl. 198-37) This invention relates to conveyors and especially conveyors of the type using a belt.

This application is a division of the United States patent application Serial No. 514,228, filed June 9, 1955 (now Patent No. 2,895,593), entitled Conveyors.

An important object of the present invention is the provision of a conveyor construction using a. belt with anti-friction surfaces provided preferably at both sides of the belt so that an article to be conveyed may rest partially on the belt and partially on the anti-friction surfaces. sion of a conveyor using a relatively narrow endless belt having disposed at opposite sides thereof a series of rollers which maybe mounted on anti-friction bearings.

'A further object of the invention is the provision of a conveyor using a relatively narrow endless belt having disposed at opposite sides thereof fixed anti-friction surfaces.

Another very import-ant object of the invention is the provision of means to adjust the position of the belt with respect to the anti-friction surfaces at either side thereof and to control the gripping a'ctionof the belt on the article to be conveyed. Such adjustment and control may be accomplished manually or automatically, and it is Within the contemplation of the invention to use me chanical or electrical means or a combination of both to accomplish such adjustment. It is, of course, possible to adjust the belt to such a position, that an article to be conveyed is at rest and supported solely by the antifriction means at either side ofthe belt or to vary the gripping contact of the belt with the larticleas desired.

A feature of the invention is the use of a flat belt having a substantially wedge-shaped depending portion for tion and features wide flanges extending outwardly at opposite sides of the grooved portion of the. pulley to insure adequate support for the belt.

A further feature of the invention is the flexibility of use of the conveyor unit which may be attached to a like conveyor unit, or even to a conveyor unit of a difierent type.

An additional feature is that the conveyor unit may be driven by :a detachable motor coupling unit and, in order to connect conveyor units in tandem, tail and head pulley shafts respectively of'adjoining conveyors may be coupled together by a detachable coupling unit.

The conveyor unit of the present invention may even find utility as a gravity conveyor by detaching the motor unit and, if desirable, connecting to the appropriate pulley shaft of the conveyor :a regulatable braking means which is preferably of the fluid type. 4

Another object of the invention is ;the-provi Patented Sept. 17, 1963 Besides its greatfiexibility of use, a conveyor embodying the present invention may be relatively light in weight, since it makes possible the use of a narrow belt in combination with the antiafriction surfaces which permit free sliding movement of an article to be conveyed which ex tends beyond the edges of the belt. A disadvantage of prior art beltconveyors is that there are noopen portions in the conveyor'through which switching members or other mechanical accessories may be inserted. This disadvantage is obviated in the present invention since the belt occupies only a relatively small portion of the upper part of the conveyor leaving ample open spaces at either side of-the belt due to the use of spaced antifriction surfaces.

Yet another advantage of the present invention is that, since there is adequate open space at either side of the belt, a carton or other article may be readily handled by an operator who may place his fingers below such a carton without firsttilting the carton, which is rather difficult with a wide belt which does not leave exposed any part of the underportion of the article. This is also a safety factor.

One exemplary situation in which the automatic adjustment of the belt finds utility is a conveyor system using a plurality of conveyor units in tandem. As sometimes occurs, an article in advance of the conveyor unit being considered is stopped so that -a series of articles ,pile up at the rear of said article and exert great pressure. By means of the automatic adjustment of the present invention it is possible to reduce the forward thrust on the piled up articles, or even to stop the thrust entirely by lowering the belt sufficiently, as above indi-- tion with roller wheels beneath and at opposite sides of the belt.

FIG. 3, is a detailed view of means for adjusting the belt tension.

FIG. 4 is an end view of a pulley showing the beltin engagement therewith. I g v FIGS. 5, 6 and 7 are schematic illustrations of a de tachable coupling for coupling together two -conveyor units, FIG.- 5 being aside view, FIG. Gbeing a top view, and FIG. 7 being a detailed view of the coupling proper. FIG. 8 illustrates a fluid drive braking arrangement for a gravity conveyor.

FIG. 9 illustrates a fluid pump braking arrangement for gravity conveyor.

FIG. 10, is a partial perspective view showing a belt in combination with fixed anti-friction surfaces at opposite sides' of the belt.

FIG. 11 is a partial perspective view showing the use of continuous anti-friction ribs or rails.

FIG. 12 is a partial perspective view showing fixed anti-friction surfaces for supporting and guiding the belt.

FIG. 13 illustrates a conveyor unit having an adjustable belt with the belt adjusted to a raised position.

FIG. 14 illustrates a conveyor unit having an adjustable belt with the belt adjusted to a lowered position.

FIG. 15 is a partial perspective view illustrating particularly the center frame used for raising and lowering the belt.

FIGS. 16, 17 and 18 are detailed views showing arrangements for moving the center frame.

FIGS. 19 and 20 are detailed views showing arrangements for automatically adjusting the position of the belt; and

' FIG. 21 is a detailed view showing an arrangement for manually adjusting the position of the belt.

With reference first to FIGS. 1 to 4, the conveyor unit is shown employing a relatively narrow belt 11 which is mounted on pulleys 12 at opposite ends of the conveyor unit. The pulleys 12 are attached to shafts 13 suitably journalled in the apparatus. The shaft 13 used as the driving shaft has projecting upwardly therefrom toward one end a pin 14, better seen in FIG. 7, so that when the portion of the slotted opening 15 of the coupling collar 16 of a detachable motor unit 17 extending to the right in FIG. 1 is in alignment with the pin by sliding the motor unit to the right, driving engagement will be effected when the motor rotates to lock the pin in the portion of the coupling extending transverse to the axis of shaft 13.

Attached to the conveyor frame 18, which may be of aluminum or other light weight material, is a series of shafits 19 extending transverse to the direction of travel and supporting at opposite sides of the belt the rollers 20 and beneath the belt rollers 21 oflesser diameter than the rollers 20 whereby the outer surface 23 of the belt is substantially in the plane A of the upper surface of the rollers 20.

By particular reference to FIGS. 2 and 4, it will be observed that the belt includes a wedge-shaped depending portion 24 in engagementwith the groove 26 of pulley 12 and further that the pulley includes flanges 27 which provide adequate support for the belt. The rollers 21 closest to the central portion of the belt are preferably placed at opposite sides and contiguous with the depending portion 24 of the belt to assist in guiding the belt along its course in addition to providing support for the belt. The rollers 20 and 21 are preferably of the type having anti-friction bearings, sometimes referred to as skate wheels.

It may also be desirable to mount the rollers 20 which are at opposite sides and closest to the edges of the belt somewhat remote from said edges so that an article to be conveyed may tend to bow in at the center, thus insuring an adequate gripping contact of the article with the upper surface 23 of the belt. Additionally, if there is some wear on the upper surface of the belt, gripping engagement will still be assured.

The rollers 20 may comprise only a single roller on each shaft 19 at opposite sides of the belt or there may be two or more rollers mounted at each side of the belt. In FIG 1 the rollers are shown mounted in staggered formation with two rollers 20 mounted on alternate shafts and only a single roller 20 on the intervening shafts 19 considering, of course, only one side of the belt. It isalso feasible to use only a single roller 21 below the belt 11 on either side thereof, or to arrange these rollers in any convenient pattern.

It is apparent from the aforementioned description that an article to be conveyed may be placed on the conveyor with the central portion of its lower surface in driving engagement with gripping surface 23 of the belt 11 and with its outer portion of its lower surface resting on the rollers 20. When the motor is operated, the belt will transport the article while outer portions of the lower. surface of the articles will engage the rollers 20 at spaced points and ride freely thereover, the rollers adding a minimum to the total load and usually less than that contributed by the prior art wide and heavy belt underlying substantially the entire surface of the article to be conveyed.

It might be mentioned here that it is conventional prior art practice in the usual wide belt conveyor to place rollers beneath the belt to insure that support is provided at all points beneath the belt so that rollers equivalent to rollers 21 are already present in such arrangements. In other words, the rollers 20 are not necessarily additional items of the conveyor but items normally present in belt conveyors.

In FIG. 3 is shown an arrangement for adjusting the belt tension comprising an idler roller 31 journalled on bracket 32 which has threaded therein a driving screw 33 which may be suitably rotated to vary the position of bracket 32 which is mounted for sliding movement to thus vary the tension on the belt 11 as desired.

In FIGS. 5, 6, and 7 is shown a detachable coupling 36 whereby two conveyor units 10 and 10' may be connected together in tandem in driving engagement. The same type of bayonet coupling described earlierufor the detachable motor unit may be utilized comprising the.

bayonet coupling collars 37 projecting from the detachable coupling and respectively suitably attached to shafts 38. The shafts carry the sprockets 39 in engagement with the chair schematically shown at 41. It is obvious, especially from the previous description of the motor unit, that the coupler 36 may be placed in driving engagement with shafts 13 of separate conveyor units by moving the collars 37 over said shafts to engage the pins 14 on the shafts, rotation of the shafts locking the pin in the slotted portion of the bayonet coupling which is normal to the axis of shafts 38. The central opening of the collars 37 are, of course, appropriately machined to insure a snug fit of the collars of the shafts 13.

If it is desired that the conveyor be utilized for conveying via gravity, the motor unit 17 may be withdrawn and there may be connected in driving engagement with one of the shafts 13 a fluid braking device 44 shown schematically in FIG. 8, whichmay be suitably adjusted in any conventional manner such as by varying the relative axial positions of the rotor 46 and stator 47, or by. angular adjustment of the blades in the rotor or stator. Thus, as an article descends, it will cause the belt to move in its endless path rotating the pulley 48 on shaft '13 to drive the belt 49 to rotate the rotor 46 and shaft 51 against the retarding action of the fluid between the rotor 46 and stator 47.

A similar result may be accomplished by use of the fluid pump 50 according to FIG. 9 'by coupling one of the impellers 53 to a pulley shaft 13 and adjusting the valve 54controlling the fluid proceeding over one conduit 56 to the housing 57 where it is pumped in a circuitous course over the other conduit 56, and back through valve 54. It is obvious that, by adjusting the constriction of the valve opening, the retarding action of the fluid pump may be adjusted.

Turning now to FIG. 10, it will be seen that, for the wheels 20 of FIGS. 1 and 2, may be substituted at either side of the belt a series of fixed anti-friction projections 61 suitably mounted at the top portion 62 of the conveyor.

In the place of the projections 61 may be, substituted the rib or rail members 63 projecting upwardly from a member 64 as shown in FIG. 11. These ribs or rail members 64 may extend at either side and along substantially the entire length of the upper pass of the belt.

In place of rollers 21 there may be used below belt 11, as shown in FIG. 12, a series of anti-friction ribs or rails which may be continuous orarranged in any convenient pattern.

Now to be described is the embodiments of the invention devoted to varying the gripping action of the belt in proportion to the load or the position of the belt with respect to the plane of the anti-friction surfaces at either side of the belt. In FIG. 13, the belt is shown in a raised position in gripping engagement with the cartons to be conveyed, whereas in FIG. 14 the belt is shown ina lowered position out of engagement with the cartons. In FIG. 14, therefore, the gripping engagement has been reduced to zero.

The belt 11 shown in FIG. 15, which also brings out that the surface thereof may have excellent gripping qualities, is supported during the upper pass once more by rollers 21 but in the present case the rollers 21 are no longer mounted on the shaft -19 carrying the larger outer rollers 20, but instead, are mounted on shafts 71 carried by a separate movable center frame 72. The center frame is mounted on the central portion of the shafts .19 with the sloping cam surfaces 73 at opposite sides of the frame resting on the shafts and free to move thereon so that when the center frame 72 is shifted to the right as viewed in FIG. 15, the center frame will be lowered, whereby the rollers 21 will exert less pressure beneath the under portion of belt '11, and the belt in turn tends to exert less gripping action on the article to be conveyed. Ultimately, of course, further movement to the right will lower the belt to such position that it no longer engages the article to be conveyed. When the center frame is shifted to the left, the opposite condition ensuesthe center frame moving upwardly and pressing the rollers more firmly against the under portion of belt 11 and increasing the gripping action of the belt on the article to be conveyed as the rollers are raised. The position of the frame 72, and hence the gripping engagement of the belt 11, may be controlled as described hereafter in connection with FIG. 21.

' FIG. 16 shows one arrangement for controlling the position of the belt or gripping action thereof wherein there is attached to the center frame a depending member 76 in operative engagement with the armature 77 of solenoid 78. The solenoid 78 may be actuated by means of switch 79 which may be controlled manually or by a relay and may even form part of a remote control system or a system using automation. There may be an additional depending member like 76 at the opposite side of the center frame 72, the depending members being interconnected by means of a plate, or otherwise.

In FIG. 17 the cam surfaces 73 may be dispensed with, the movement of the frame being controlled by levers 81 suitably pivoted at 82 and 83. Of course, there may be a further set of levers 82 (not shown) mounted at the other side of the center frame 72. It is understood that any suitable mechanism may be attached to the center frame 72 or the levers 81 to move the center frame together with rollers 21 to the desired position beneath the belt.

A further mounting for the center frame 72 is shown in FIG. 16 where again the cam surfaces 73 are dispensed with. In this case, the opposite sides of the center frame include slotted portions 85 in engagement with the shafts 19. Compression spring members 84 which also may, if desired, be placed at opposite sides of the center frame 72 urge the center frame in :an upward direction. The compression springs 84 may be so selected and suitably adjusted to exert the desired upwardly acting force on the center frame so that the forward thrust on the article to be conveyed is controlled.

FIGS. 19 and 20 show arrangements automatically operative to adjust the position of the belt 11. In FIG. 19 the belt 11 is driven by the pulley 12 mounted on shaft 13. Also, attached to the shaft 13 is the sprocket 91 in driving engagement with the chain 92 which passes also around the sprocket 93 mounted on shaft 94 driven by the motor 96. Mounted on fixed sleeves 97 and 100 of the conveyor unit is a rod 98. The rod 98is surrounded at one portion thereof by a spring 99 which presses against the sleeve 100 under the action of the adjustable nut 101. The rod 98 is attached at 102 to the depending portion 103 of the center frame 72. Attached to the rod 6 93 are a pair of spaced shafts 104 carrying the sprockets 106 and 107 which are in engagement with the chain 92, as shown in FIG. 19. When the load on the belt 11 increases, the chain portion at the right as seen in FIG. '19

tends to straighten out, pushing against the sprocket 107 and thereby moving the rod 98 to the right against the influence of spring 99. This, of course, moves the center frame 72 to the right so that the pressure of rollers 21 against the under portion of the belt 11 is lessened. The mechanism may operate in the reverse manner when a decreased load condition is encountered.

FIG. 20 is very similar to FIG. 19"except that now, instead of the rod 98, there is provided a rod 111 attached to a lever 112 carrying anti friction wheels 113, only one of which is shown, which bear against plates '114 depending from center frame 72. Further in the figure the sprockets 106 and 107 (not shown) are mounted between plates 116, only one of which is shown.

It is possible to arrange the movement of the center frameso that under-very abnormal conditionsof load the position of thewheels 21 may be lowered to such an extent that the article to be conveyed rests solely on the outer rollers 20, which means that the belt is actually placed out of driving engagement with the article. There may be provided a limit switch engageable by anyirno vable part associated with the movement of the belt when a particular position is reached, to control or operate the' motor.

It has been found that, after compensation for a load change has been made, the center frame tends to hold the adjusted position. It will be noted that, since sprock-- ets 106 and 107 are both mounted on the rod (FIG. 19),

movement of sprocket 107 will be accompanied by a like movement of sprocket 106 which will maintain its driving engagement with the chain 92. As pointed out hereto-- fore, the adjustable nut 101 may be used to adjust the tensionof the spring 99, whereby the shaft will movewhen a predetermined load is applied to the'belt. T

FIG. 21 illustrates how the position of the belt 11 or thegripping action of the belt may be varied not only in one conveyor unit '10 but also in an adjoining conveyor unit.

ing a hand gripping portion 124. Asthe handle is moved clockwise in FIG. "21, the eccentric moves'against plate' 126 attached to member 127 which may be suitably fa'stened'to centerframe 72. As the plate 126 moves, it

carries with it the rod 128 against the action of compression spring 129, the rod 128 being suitably mountedforj sliding movement in sleeve 131. 'The center frame 72 of conveyor'unit 10 is simultaneously movable with the center frame 72 of adjoining con veyor unit 10' by reason of the link connection which includes a slotted portion 133 wherein adjustment may be made by means of the screw 134. Center frames 72 of adjoining sections may also be adjusted to different eleva tions, if desired. Also, frame 72 may be so constructed that :one .end is at a slightly higher elevation than the other end, with respect to wheels 20.

Shaft 122 may, of course, include a ratchet witha 00- operating detent so that the shaft may be held in an adjusted intermediate positionyif desired. a

While the use of a single belt has been shown, it is obvious that a plurality of belts may be used. For example, a pair of spaced belts could be used with anti-friction surfaces mounted intermediate the belts, and desired, additional anti-friction surfaces may be mounted In this case, an eccentric 121 is mounted on a suit-' ably supported shaft 122 which carries a handle 1'23 hav-" having The belt may be constructed of a nrulti-ply canvas with a ribbed or embossed surface of rubber for good gripping action, or if desired for some applications, a smooth surface.

Various departures may be made in the embodiments shown without departing from the spirit of the invention.

We claim:

1. In a conveyor having a supporting surface adapted to support articles disposed on said conveyor and a power driven propelling member in substantially the same plane as said support surface; a vertically adjustable support means for said propelling member; means having an element for determining the accumulated drag imposed on said propelling member by articles disposed on said conveyor and a movable member for translating the drag detected by said element into vertical adjustment of said support means and of said propelling member with respect to said supporting surface for maintaining tension on said propelling member at a predetermined value.

2. In a conveyor having a supporting surface adapted to support articles disposed on said conveyor, said sup porting surface having a central lane extending lengthwise therethrough and a power driven propelling member in said lane in substantially the same plane as said supporting surface; a vertically adjustable support means for said propelling member; means having an element for determining the accumulated drag imposed on said propelling member by articles disposed on said conveyor and a movable member for translating the drag detected by said element into vertical adjustment of said support means and of said propelling member with respect to said supporting surface for maintaining tension on said propelling member at a predetermined value.

3. In a conveyor having a supporting surface of freely rotatable article supporting members adapted to support articles disposed on said conveyor, said supporting surface having a lane extending lengthwise therethrough and a narrow power driven propelling member in said lane in substantially the same plane as said supporting surface; a vertically adjustable frame beneath and supporting said propelling member; first means for raising and lowering said frame; second means having an element for detecting the accumulated drag imposed on said propelling member by articles disposed on said conveyor and a member operatively connected to said first means for effecting vertical adjustment of said frame and of said propelling member with respect to said article supporting members in response to the accumulated drag detected by said element for maintaining tension on said propelling member at a predetermined value.

4. In a conveyor having a supporting surface of freely rotatable article supporting members adapted to support articles disposed on said conveyor, said supporting surface having a lane extending lengthwise therethrough and a narrow power driven propelling member in said lane in substantially the same plane as said supporting surface; a vertically adjustable frame beneath and supporting said propelling member; a support element for said frame causing the raising and lowering of said frame as said frame is reciprocated lengthwise; means having an element for detecting the accumulated drag imposed on said propelling member by articles disposed on said conveyor and a member operatively connected to said frame and said element for shifting said frame vertically in response to the tension on said propelling member.

5. In a conveyor having a supporting surface adapted to support articles disposed on said conveyor and a power driven propelling member in substantially the same plane as said support surface; a vertically adjustable support for said propelling membenmeans having a member for effecting the raising and lowering of said support'and an element for detecting the drag imposed by an article on said propelling member; said raising and lowering member being under the command of said element for effecting vertical adjustment of said support in response to the drag of the article.

'6; In a conveyor having a supporting surface adapted to support articles disposed on said conveyor and a power driven. propelling member in substantially the same plane as said support surface; a vertically adjustable support for said propelling member; means having a member for effecting the raising and lowering of said support and an element having means for detecting the accumulated drag imposed on said propelling member by articles disposed on said conveyor; said raising and lowering member being under the command of said element for effecting vertical adjustment of said support and of said propelling member with respect to said supporting surface for varying the magnitude of the bearing pressure between said propelling member and the article.

7. In a conveyor having a low friction supporting surface for the transport of articles disposed on said con veyor and a power driven propelling member; first means controlling the position of said propelling member with respect to articles on said supporting surface; second means having an element for detecting the accumulated drag imposed on said propelling member by articles disposed on said conveyor and a member responsive to said element and operatively connected to said first means for shifting said propelling member with respect to the articles on said supporting surface for maintaining the tension on said propelling member at a predetermined value.

8. In a conveyor having a low friction article supporting surface for the transport of articles disposed on said conveyor and a power driven propelling member; a movable frame controlling the position of said propelling member for moving said propelling member toward and away from articles on said supporting surface; a support for said frame causing the movement of said frame toward and away from said articles; means having an element for detecting the accumulated drag imposed on said propelling member by articles disposed on said conveyor and a member operatively connected to said frame and said element for shifting said frame toward and away from said articles in response to the tension on said propelling member for maintaining the tension on said propelling member at a predetermined value.

9. In a conveyor having a low friction article supporting surface for the transport of articles disposed on said conveyor and a power driven propelling member; a movable frame controlling the position of said propelling member for moving said propelling member toward and away from articles on said supporting surface; a support for said frame causing the movement of said frame toward and away from said articles; means having an element for detecting the accumulated drag imposed on said propelling member by articles disposed on said conveyor and a member responsive to said element for shifting said frame toward and away from said articles in response to the tension on said propelling member for maintaining the tension on said propelling member at a predetermined value.

10. In an accumulator conveyor having an article supporting surface and a driven activating member, means for supporting said activating member and means responsive to drag imposed by an article on said driven activating member, said responsive means comprising: first means having a pulley element over which said driven activating member passesand at detecting element for detecting the tension applied to said driven activating member; said supporting means being movable to shift the position of said driven activating member for moving said driven activating member toward and away from article moving position for adjusting the propelling pressure exerted on an article by said driven activating member and maintaining the total tension applied to said driven activating member within a predetermined maximum; connecting means between said supporting means and said detecting element for the transfer to and utilization at said supporting means of information received by said detecting element.

11. In an accumulator conveyor having a supporting surface adapted to support articles disposed on said conveyor, a power driven propelling member in substantially the :same plane as said supporting surface, a vertically adjustable support for said propelling member, first means for effecting vertical movement of said support and means responsive to drag imposed on said propelling member by an article on said conveyor, said responsive means comprising: :an element for detecting the accumulated drag imposed on said propelling member by articles disposed on said conveyor and a linkage connected to both 10 said detecting element and said support for translating the drag detected by said element into vertical movement of said support and of said propelling member with respect to said supporting surface for maintaining tension on said propelling member at a predetermined value.

References Cited in the file of this patent UNITED STATES PATENTS 1,209,021 Phillips Dec. 19, 1916 1,598,099 Murray Aug. 31, 1926 1,857,566 Perry May 10; 1932 

1. IN A CONVEYOR HAVING A SUPPORTING SURFACE ADAPTED TO SUPPORT ARTICLES DISPOSED ON SAID CONVEYOR AND A POWER DRIVEN PROPELLING MEMBER IN SUBSTANTIALLY THE SAME PLANE AS SAID SUPPORT SURFACE; A VERTICALLY ADJUSTABLE SUPPORT MEANS FOR SAID PROPELLING MEMBER; MEANS HAVING AN ELEMENT FOR DETERMINING THE ACCUMULATED DRAG IMPOSED ON SAID PROPELLING MEMBER BY ARTICLES DISPOSED ON SAID CONVEYOR AND A MOVABLE MEMBER FOR TRANSLATING THE DRAG DETECTED BY SAID ELEMENT INTO VERTICAL ADJUSTMENT OF SAID 